Composite materials, i.e. tooth replacement materials containing binders in the form of hardenable, generally organic substances, are in the process of becoming the standard filling materials in dentistry. Therefore, the advantages and disadvantages of these materials acquire a central significance. An essential disadvantage is that up to now, all composite materials adhere more or less to the instrument which is used to apply or shape them. Thus, for example, the material has a stubborn tendency to be drawn off from the edges of the cavity. Since there is a trend to conform the composite materials as closely as possible to the final shape while they are still soft, in order to minimize the finishing work, this effect is becoming even more disturbing.
There have been numerous attempts to solve this problem. The most diverse materials have been used for the manufacture of instruments for composite materials, their surfaces have been treated, and many different shapes have been designed. Up to now, all these efforts have been unsuccessful.
The dentist mostly evades the difficulty by wetting the instruments with liquid composite bonding, thereby eluding the adhesion. As a result, however, the filling material is diluted and loses in quality. This is why this method is not recommended in science and research.
It will probably never be possible to eliminate the adhesion completely; neither would it be desirable. The composite material should adhere to the instrument to such a degree that a safe transport of the material from the dispensing location to the tooth is ensured without the risk that the portion falls off.
Some of the methods allowing to adjust the adhesion of the composite material on the instrument consist in coating the instruments with Teflon (C. M. Sturdevant, R. E. Barton, C. L. Sockwell, and W. D. Strickland (ed.), "The art and Science of Operative Dentistry", 2nd edition, C.V. Mosby Company, St. Louis, Toronto, Princeton, 1985, p. 365), wetting them with alcohol (J. Kanter, R. E. Koski, and J. E. Gough, The Journal of Prosthetic Dentistry 41 (1979), pp. 45-50), and in providing a titanium nitride surface coating (J. G. Steele, J. F. McCabe, and I. E. Barnes, J. Dent. 19 (1991), pp. 226-229). However, the application of separating agents (such as alcohol) requires an additional operation as well as the corresponding experience since the quantity of separating agent influences the adhesion and an excessive amount may alter the working properties of the composite material. If the instruments are manufactured from Teflon or coated with Teflon, the design of the surfaces and to a certain extent also the possible shapes are limited, on one hand, and the instruments are not always satisfactory in practice, on the other hand.